Studies and Monitoring

Everglades National Park

Everglades National Park (NP), Florida, has its own unique environmental concerns based on its particular ecology. Air quality studies and monitoring programs at Everglades NP focus on mercury deposition and effects. Click on the tabs below to review air quality studies and key scientific references at Everglades NP, as well as to access information on air quality monitoring in the park.

Studies & Projects

Monitoring & Data

Key References

Ongoing research in Everglades NP, Florida:

Mercury and the Endangered Florida Panther

The Florida panther (Puma concolor coryi), a state and federally-listed endangered species, has suffered severe declines in population numbers because of environmental stressors, low genetic variability, and habitat loss. Mercury contamination continues to be a suspect in the species’ poor reproductive success. Detectable levels of mercury in panthers and strong spatial gradients have been evident from surveys dating back to 1978, with the highest levels found in panthers from the Shark River Slough of Everglades NP (Roelke et al. 1991). The spatial gradients were reconfirmed more recently (Brandon et al. 2009), and Everglades NP continues to have the highest mean concentrations of mercury in panther hair and blood of all four South Florida regions studied (SFER 2011). Also, mercury in panther hair samples from the 1990s was significantly higher than in museum specimens dating back to the 1890s (Newman et al. 2004). A study in the early 2000s concluded that the risks to panthers from mercury exposure had decreased somewhat from the 1990s (Barron et al. 2004), likely because of better controls on sources of airborne mercury. However, there is evidence that high mercury-level regions in the Everglades continue to exist or could increase because of marsh restoration activities. The high mercury levels found in panthers in Everglades NP have been attributed to a preferential diet consisting predominantly of fish-eating wildlife, such as raccoons and alligators, rather than of herbivores, such as deer.

Mercury and Toxics Impacts

Everglades NP and the surrounding South Florida region have extremely high levels of mercury contamination. This is due in part to high rates of atmospheric mercury deposition from external and local sources, which include coal-burning power plants and waste incinerators, and also due in part to the area’s unusual environmental conditions. Mercury has been documented in many ecosystem components and different levels of the food chain at the park. Elevated concentrations in invertebrates, frogs, fish, wading birds, pythons, and alligators exceed environmental and human health thresholds (Guentzel et al. 1998; Krabbenhoft 2010; Rumbold et al. 2002; Rumbold 2005; Ugarte et al. 2005). Mercury contamination has been suspected in the death of some Florida panthers and attributed to high liver mercury levels (Barron et al. 2004; Roelke et al. 1991). Mercury in wading birds is at levels known to cause neurologic and reproductive impairment (Frederick and Jayasena 2010; Sundlof et al. 1994). Ongoing mercury research at the park continues to assess mercury cycling in the environment and accumulation in sediments, fish, and wildlife.

Despite many scientific accomplishments in the last decade that have improved understanding about how mercury cycles in the Everglades marsh, a significant question remains: Why is mercury in Everglades NP’s biota much higher than in biota from most everywhere else in south Florida? The park continues to collect and provide tissue, feather, or unhatched egg samples from several species, and water and sediment samples, for mercury analysis to answer this question. Mercury monitoring at Everglades NP may also soon be expanded to include wading birds, such as the woodstork—a federally-listed endangered species.

Studies have been conducted on other airborne toxics, including endosulfan. Elevated levels of this agricultural pesticide in sediment, surface waters, and native fish in the Everglades and nearby Biscayne Bay, and in several western national parks, led to widespread public demands to ban endosulfan. EPA recently banned the chemical and is currently negotiating a phase out of endosulfan for all commercial and residential uses.

Rumbold, D. G. 2005. A probabilistic risk assessment of the effects of methylmercury on great egrets and bald eagles foraging at a constructed wetland in South Florida relative to the Everglades. Human and Ecological Risk Assessment 11 (2): 365–388.